Pattern correction method and manufacturing method of semiconductor device

ABSTRACT

A pattern correction method executed by a computer includes a first correction and a second correction. The first correction is executed by calculating a correction value, in consideration for an optical proximity effect, for edges (first edges) meeting a condition among the edges constituting a designed pattern. Subsequently, The second correction is executed for an edge (second edge) which does not meet the condition, by use of the correction value of any one of the edges (first edges) adjacent to the second edge among the first edges for which the first correction is executed, thus connecting the corrected first edge and the corrected second edge by a line segment. The pattern is corrected to a shape suitable for a mask drawing and a check with simple processing.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application P2001-398438 filed on Dec.27, 2001, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a pattern correction required inlithography processing of semiconductor integrated circuits and liquidpanels, and more particularly to a correction technology of a maskpattern for performing faithful pattern transfer to a design pattern.

[0004] 2. Description of the Related Art

[0005] In a photolithography technology used in manufacturing processingof semiconductor integrated circuit and liquid crystal panels, anoptical proximity effect has become more serious problem as anintegrated degree more increases and design rules become more critical.

[0006] An optical proximity effect is phenomenon in which the designpattern is not transferred on a wafer in the intended shape anddimension. For example, such phenomenon that the dimension of a linepattern reduces in its long side direction or the corner portion of anL-shape line pattern is transferred in a round shape is the typicaloptical proximity effect. Although the optical proximity effect hasoriginally meant an effect due to optical factors in pattern transfer,now it means an effect caused through the entire wafer processes.

[0007] When the optical proximity effect arises, deviation between thedesign pattern and a pattern actually formed occurs, and it isimpossible to achieve desired device performance. Therefore, an opticalproximity effect correction (OPC) is required to reproduce a patternhaving the designed dimension and shape on a wafer. The opticalproximity effect correction means changing selectively the shape of thepattern or the like on a mask in advance in consideration of a processconversion difference.

[0008] Various techniques have already proposed and carried out for theoptical proximity effect correction. There are a simulation-based and arule-based (alternatively referred to as a model based) methods as amethod to prepare mask data by automatically executing the opticalproximity effect correction (hereinafter referred to as “OPC” dependingon the situation) on design data. The simulation-based OPC is a methodin which an optical image in a mask pattern layout is calculated beforea correction, a portion deviating from the pattern is detected, and thedetected portion is corrected. This method shows high correctionprecision although much calculation amount is required, and is used forcalculating a correction value for a line segment or an edge havingimportance among line segments and edges composing the pattern.

[0009] The rule-based OPC is a method to execute a correction such asmask bias according to rules. This method showing a high processingspeed, determines the correction value according to predetermined rules,for each edge of a figure contained in a design layout to apply thecorrection value for an optical proximity effect correction.

[0010] In the conventional optical proximity effect correction, edgesnot meeting predetermined conditions, for example, edges having lengthshorter than predetermined values (hereinafter referred to as “minuteedges”), are excluded from being subjected to the OPC. The OPC isexecuted only for edges having length longer than predetermined value.As a matter of course, the minute edges originally exist in the stage ofdesign data, and they often occur as results of repeatedly performedcomplicated and minute pattern data processing prior to the OPC. If theminute edges exist, minute projections, minute hollows, acuteprojections and acute hollows are caused by the OPC itself and patterndata processing subsequent to the OPC. They are factors adverselyaffecting a mask drawing and a check.

[0011]FIGS. 1A and 1B illustrate the examples of occurrence ofprojections and hollows caused by the conventional optical proximityeffect correction. In FIG. 1A, only edges 1002 and 1003 having lengthlonger than predetermined values are objects of the OPC in a pattern1001 shown by solid lines, which has not subjected to the OPC yet. TheOPC to thicken the pattern was executed for the edges 1002 and 1003while leaving a minute edge 1004 excluded from the object of the OPC atan initial position. As a result of the OPC, the corrected pattern 1005illustrated by the dotted lines is obtained. In the pattern 1005 afterthe OPC, the minute hollow 1006 occurs.

[0012] In the case of FIG. 1B, in the pattern 1010 illustrated by thesolid lines, which has not subjected to the OPC yet, the edges 1012 and1013 meeting conditions are similarly objects of the OPC, and the minuteedges 1014 and 1015 are excluded from the object of the OPC. As aresult, the pattern 1020 illustrated by the dotted lines is obtained. Inthis case, an acute projection and a slanting slit occur as illustratedby the circle A.

[0013] These minute projections (acute pattern) and these minute hollowsincrease a data amount uselessly, and decrease mask drawing precision.In addition, a mask drawing time becomes much longer. In checking maskdefects process, they are apt to be detected as suspected failure, andmuch time and labor are needed for error detection.

[0014] In order to erase minute unevenness caused by the OPC, a methodhas been known, in which a slightly thick/thin bias or a slightlythin/thick bias is applied to the whole of a layout after the OPC, andminute projections and minute hollows are erased. However, projectionsand hollows may be caused additionally at unexpected spots by performingsuch bias processing. Also disadvantageous deformation such as a shortand slit may occur. Moreover, there are many shapes having projectionsand hollows that are not erased only by the bias processing.

[0015] For example, as shown in FIG. 2A, the pattern 1030 obtained bythe OPC processing has the minute hollow 1031 and the minute projection1032. When slightly thick bias is first applied to the pattern 1030, thehollow 1031 is made to be flat, and the pattern 1035 illustrated in FIG.2B is obtained. When slightly thin bias is further applied to thepattern 1035, the pattern 1037 having dimensions which are almost equalto those of the initial pattern is obtained as shown in FIG. 2C. In thissituation, although the hollow 1031 is erased, the extremely acutehollow 1033 occurs.

[0016] When slightly thin bias is further applied to the pattern 1037,the pattern 1039 in which the projection 1032 is erased is obtained asshown in FIG. 2D. Then, by applying slightly thick bias to the pattern1039, the pattern 1041 in which the hollow 1031 and the projection 1032are finally erased is obtained as shown in FIG. 2E.

[0017] However, the acute hollow 1033 illustrated by the circle B is noterased in spite the bias processing is executed over and over again. Theacute hollow on the mask pattern is undesirable because this acutehollow is a cause of suspected error detection in checking the maskprocess as well as a cause of a decrease in mask drawing precision.

[0018] On the other hand, when the correction values for the respectiveminute edges, which are left at initial positions in the pattern, andunevenness are individually calculated by the simulation-based methodafter the OPC processing, the calculation amount and the processing timeare enormous, and such individual calculations are impractical

SUMMARY OF THE INVENTION

[0019] A pattern correction method of a first aspect according to thepresent invention is the one executed by a computer, which includesexecuting a first correction and a second correction. The firstcorrection is executed by calculating correction values for at least oneof first edges meeting conditions among the edges constituting adesigned pattern in consideration for an optical proximity effect andcorrecting the one or more first edges with the correction values. Thesecond correction is executed for a second edge which does not meet theconditions, by correcting the second edge with the correction value ofany one of the first edges adjacent to the second edge among the firstedges for which the first correction is executed. Then the correctedfirst edge and the corrected second edge are connected by a linesegment.

[0020] The conditions are, for example, as follows. The length of anedge is equal to a predetermined values or more, an edge does not form avertical or slanted step difference which is shorter than apredetermined height, and so on. In this case, the first correction(optical proximity effect correction) is executed, and then the secondcorrection is executed for a minute edge which does not meet theconditions.

[0021] A pattern correction method of a second aspect according to thepresent invention is the one executed by a computer. In the methodincludes designing a pattern to be formed on a wafer; and executing acorrection for at least one of edges meeting conditions among edgesconstituting the pattern in consideration for an optical proximityeffect are performed. Next, deciding whether or not the correctedpattern includes minute pattern having no effect on a transferred imageonto the wafer; executing bias processing in combination of bias forthickening the whole of the pattern after the correction and bias forthinning it when the corrected pattern includes the minute pattern areperformed. Then after the bias processing, a logic operation isexecuted, thus erasing an acute pattern caused by the bias processing.

[0022] A manufacturing method of a semiconductor device of a thirdaspect according to the present invention includes preparing design datain which patterns formed on a semiconductor wafer are designed forrespective layers, inputting the design data for each layer, andpreparing mask data for the pattern included in each design data. Inpreparing the mask data, a first correction is executed by calculatingcorrection values for at least one of first edges meeting conditions inconsideration for an optical proximity effect, and a second correctionis executed for a second edge which does not meet the conditions, by useof the correction value of the first edge adjacent to the second edgewhich does not meet the conditions among the first edges for which thefirst correction has been executed, and the corrected first edge and thecorrected second edge are connected. Furthermore, the method includespreparing a mask based on the mask data; and transferring the patternonto the semiconductor wafer by use of the mask.

[0023] A manufacturing method of a semiconductor device of a fourthaspect according to the present invention includes preparing design datain which patterns to be formed on a semiconductor wafer are designed forrespective layers; inputting the design data for each layer, andpreparing mask data for the pattern included in each design data. Inpreparing the mask data, edges meeting conditions are corrected inconsideration for an optical proximity effect. Further, the methodincludes deciding whether or not the pattern after the foregoingcorrection includes minute pattern having no effect on a transferredimage onto the wafer; executing bias processing in combination of biasfor thickening the whole of the pattern after the correction and biasfor thinning it when the corrected pattern includes the minute pattern.Furthermore the method includes executing a predetermined logicoperation after the bias processing, thus erasing an acute patterncaused by the bias processing; preparing a mask based on the mask dataprepared in the foregoing manner; and transferring the pattern onto thesemiconductor wafer by use of the mask

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIGS. 1A and 1B are plan views illustrating pattern having minutehollows caused by a conventional OPC (optical proximity effectcorrection).

[0025]FIGS. 2A to 2E are plan views illustrating pattern having acuteportions caused by conventional mask bias.

[0026]FIGS. 3A to 3C are plan views illustrating a pattern correctionmethod according to a first embodiment of the present invention.

[0027]FIGS. 4A to 4C are plan views illustrating variations of thepattern correction method according to the first embodiment of thepresent invention.

[0028]FIGS. 5A and 5D are plan views illustrating a pattern correctionmethod according to a second embodiment of the present invention.

[0029]FIGS. 6A and 6B are plan views for explaining steps in FIG. 5D indetail.

[0030]FIGS. 7A to 7C are plan views illustrating variations of thepattern correction method according to the second embodiment of thepresent invention.

[0031]FIGS. 8A to 8D illustrate a pattern correction method according toa third embodiment of the present invention, which are plan viewsillustrating an effective method as pre-processing for OPC particularly.FIG. 8E is a plan view illustrating a pattern after the correction, as acomparison example, which is obtained by performing only theconventional OPC processing.

[0032]FIGS. 9A to 9C illustrate a pattern correction method according toa fourth embodiment of the present invention, which are plan viewsillustrating the pattern correction method capable of coping with therule check of a mask design.

[0033]FIG. 10 is a flowchart illustrating the pattern correction methodcorresponding to FIGS. 9A to 9C.

[0034]FIGS. 11A to 11C are plan views illustrating variations of thepattern correction method according to the fourth embodiment of thepresent invention.

[0035]FIG. 12 is a flowchart illustrating the pattern correction methodcorresponding to FIGS. 11A to 11C.

[0036]FIGS. 13A to 13G are plan views illustrating a pattern correctionmethod according to a fifth embodiment of the present invention.

[0037]FIGS. 14A to 14G are plan views illustrating variations of thepattern correction method according to the fifth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] First Embodiment

[0039]FIGS. 3A to 3C illustrate a pattern correction method according toa first embodiment of the present invention. This embodiment will bedescribed by taking as an example a pattern correction method forperforming processing using a computer on which, for example, computeraided design (CAD) software operates. As shown in FIG. 3A, a case wherethe design pattern 10 including the minute edge 11 is processed isconsidered. The pattern 10 is a figure composed of only horizontal andvertical lines extending in the X and Y-directions.

[0040] As shown in FIG. 3B, the minute edge 11 is excluded from anobject of OPC regarding it as an edge which is shorter than apredetermined length, and corrected positions of the edges 12 to 15which meet conditions are calculated based on an ordinary OPCprocessing. Based on the calculation results, the pattern 10 is expandedby predetermined amounts in the X and Y-directions thus giving a pattern20 after the OPC, which is illustrated by dotted lines.

[0041] The OPC correction value is calculated in simulation inaccordance with characteristics of aimed edges (e.g. required precision)and positional relation with circumferential patterns. Accordingly, inFIG. 3B, for example, the OPC correction value (Y-coordinate value afterthe correction) of the edge 12 is set to be larger than the OPCcorrection value (Y-coordinate value after the correction) of the edge13. Furthermore, when the peripheral patterns are positioned near theedge 13, the correction pattern 20 in which the correction value for theedge 13 is made small is obtained as shown in FIG. 3B. When theperipheral patterns are positioned near the edge 12, the correctionvalue of the edge 12 is sometimes small.

[0042] In this stage, since the minute edge 11 remains at the initialposition, as it is not processed, the pattern 20 after the OPC includesthe minute hollow 21.

[0043] Next, as shown in FIG. 3C, simple processing is executed for theminute edge 11 that was excluded from the object of the OPC, by use ofthe results of the OPC processing. Specifically, the minute edge 11 ismade to be coincident with the OPC correction value (Y-coordinate valueafter the OPC correction) of any one of the adjacent edges 12 and 13extending the same direction as that of the minute edge 11 (in theexample of FIG. 3C, the X-direction). In the example of FIG. 3C, theminute edge 11 is made to be coincident with the smaller OPC correctionvalue (the Y-coordinate after the correction), that is the correctionvalue of the edge 13. As a result, the minute edge 11 becomes the newline segment 25 aligned with the adjacent edge 23 after the OPC, and thehollow 21 is erased.

[0044] The boundary between the new line segment 25 and the otheradjacent edge 22 after the OPC forms a step difference in theY-direction, that is, the step difference having a right angle relativeto the new line segment 25. To be more concrete, the line segment 25made to be coincident with the one adjacent edge 23 is connected to theother adjacent line 22 by a line segment extending in the directionperpendicular to the minute line segment 25. Thus, the pattern 26illustrated by the dotted line, which does not include acute portions,is obtained.

[0045] This method does not require applications of slightly thick/thinbias to the whole of the layout pattern obtained by the OPC processingof FIG. 3B. Furthermore, this method does not require the individualsimulation calculations for the minute edge 11, and the minute hollow 21can be erased by use of the correction values of the adjacent edges asobtained by the ordinary OPC. As a result; both of the data amount andcalculation amount of the mask pattern can be suppressed to the minimum,and the malfunctioning detection of suspected errors in check can beprevented.

[0046]FIGS. 4A to 4C show variations of the method of FIGS. 3A to 3C.The OPC processing of FIGS. 3A and 3B are used for this method as theyare. In FIG. 3C, though the minute edge 11 is made to be coincident withany one of the correction values of the adjacent edges after thecorrection extending to the same direction, the minute edge 11 isvirtually split at the midpoint thereof and the each side of edge 11 ismade to be respectively coincident with the correction values of each ofthe adjacent edges 12 and 13 in the method of FIG. 4C (the minute edge11 is virtually split at the midpoint thereof and both sides of minuteedge 11 match the adjacent 22 and 23). As a result, the minute edge isset to as a new line segment 27, and the left half of the edge 27 isaligned with the adjacent edge 23 after the OPC. The right half thereofis aligned with the other adjacent edge 22 after the OPC. The new linesegment 27 has a step difference extending in the Y-direction at itsmidpoint. Thus, the pattern 28 illustrated by the dotted lines, whichdoes not include an acute portion, is obtained.

[0047] The minute edge which is excluded from the object of the OPC ismade to be coincident with each of the adjacent line segments after theOPC so as to be virtually split at its midpoint, whereby the patternobtained after exposure more resembles to the design pattern.

[0048] Also in the method illustrated in FIGS. 4A to 4C, the minutehollow can be effectively erased by the correction values as they areobtained by the ordinary OPC, and the same effects as those of themethod illustrated in FIGS. 3A to 3C can be achieved.

[0049] The correction processing after the OPC illustrated in FIGS. 2Cand 3C may be combined with OPC, or alternatively may be performedseparately from the OPC. When the correction processing after the OPC iscombined with the OPC, the correction processing after the OPC can beconstructed as one pattern correction program.

[0050] Second Embodiment

[0051]FIGS. 5A to 5D illustrate a pattern correction method according toa second embodiment of the present invention. In the second embodiment,the design pattern 30 including minute slanting step differences asshown in FIG. 5A is corrected. The slanting step difference includes theminute edges 31 and 32 in the rectangular coordinate axis direction andthe minute lines 37 to 39 extending in slanting directions. In order tocorrect the pattern 30, edges meeting predetermined conditions, forexample, the edges 33 to 36 having predetermined lengths or more aresubjected to the OPC, and the respective correction values thereof aredetermined. A change amount for the edge 33 is assumed to be d1, and achange amount for the edge 34 is assumed to be d2. As a result, the edge33 that is one edge adjacent to the slanting step difference becomes theline segment 43, and the edge 34 that is the other edge adjacent to thestep difference becomes the line segment 44, thus obtaining the pattern40 illustrated by the dotted lines.

[0052] Next, as shown in FIG. 5C, simple processing is executed for thestep difference constituted by the minute edges 31 and 32 and theslanting minute edges 37 to 39 by use of the correction values obtainedin the former OPC processing. Specifically, the slanting step differencethat is excluded from the object of the OPC is moved in parallel inaccordance with the correction value of any one of the adjacent edges.Which correction value of the adjacent edge the parallel movement of thestep difference accords with depends on factors such as the correcteddirection and the relation with the peripheral patterns. In the exampleof FIG. 5C, the step difference is made to be coincident with thecorrection value of the adjacent edge 34, and the step difference ismoved in parallel by an amount equivalent to the change amount d2. Thedirection of the parallel movement is the same as the direction in whichthe adjacent edges 33 and 34 are moved by the corrections thereofpreviously performed (expansion direction). In the example of FIG. 5C,the direction of the parallel movement is the Y-direction. Thus, theminute edges 51 and 52 and slanting lines 57 to 59 after the correctionare obtained.

[0053] The slanting step difference after the parallel movement extendsfrom one adjacent edge 44 after the OPC to the other adjacent edge afterthe OPC. However, the acute hollow 45 occurs between the step differenceafter the parallel movement and the other adjacent edge 43.

[0054] Accordingly, as shown in FIG. 5D, the acute hollow 45 is erasedby a simple processing. Specifically, the other adjacent edge 43 afterthe OPC is extended in the direction thereof and at the intersectionpoint I of the adjacent edge 43 and the slanting step difference thathas been moved in parallel, the pattern is connected to the slantingstep difference.

[0055] In the example of FIG. 5D, since the difference |d1−d2| betweenthe change amount d1 for the edge 33, that is a processing amount, andthe change amount d2 for the edge 34, that is a processing amount, isequal to a step difference δ (|d1−d2|=δ), the extension line of theadjacent edge 43 after the OPC is connected to the minute edge 52 afterthe parallel movement.

[0056] The difference |d1−d2| between the correction values d1 and d2 isnot always coincident with the step difference δ because of thepositional relationship of the slanting step difference with theperipheral pattern. However, the pattern correction method of thisembodiment can be executed with the same processing even when thedifference |d1−d2| is greater or smaller than and the step difference δ,as well.

[0057]FIG. 6A illustrates a case where the difference between thecorrection values d1 and d2 is larger than the step difference δ(|d1−d2|>δ), and FIG. 6B illustrates a case where the difference betweenthe correction values d1 and d2 is smaller than the step difference δ(|d1−d2|<δ). In any cases, the other adjacent edge after the OPC isextended in the line segment direction, and connected to the slantingstep difference that has been moved in parallel at the intersectionpoint I with this step difference. Thus, a good corrected mask patternis obtained, which keeps a shape which is substantially the same as thedesign pattern.

[0058]FIGS. 7A to 7C illustrate variations of the pattern correctionmethod illustrated in FIGS. 5A to 5D and FIGS. 6A and 6B. In FIGS. 5A to5D and FIGS. 6A and 6B, shown was the mask pattern correction method inwhich the slanting step difference composed of the slanting lines andthe minute edges had relatively great significance. However, in somedesign pattern, there are cases where although the shape of a patternhas no great significance in terms of devices, the pattern connection ismade by slanting lines. In such a case, the shape of the stepdifference, which is created by the slanting lines and the minute edgesin the design pattern, is not required to keep the intact shape.Therefore, the mask pattern can be corrected with simpler processing.

[0059] Specifically, with respect to the pattern 30 of FIG. 7A, thecorrection values are determined for the edges 33 and 34 meeting thepredetermined conditions, and the pattern 40 illustrated by the dottedlines is obtained as shown in FIG. 7B. The edge 33 becomes the linesegment 43 by the correction, and the edge 34 becomes the line segment44 by the correction. The processings of FIG. 7B is the same as those ofFIG. 5B.

[0060] Next, as shown in FIG. 7C, any one of the adjacent edges 43 and44 after the OPC is extended in the line segment direction thereof.Simultaneously, the minute edge, which is excluded from the object ofthe OPC and extends from the other adjacent edge, is moved in parallelby an amount equal to the correction value of the other adjacent edge,and extended. The two line segments are connected to each other at theintersection point of the extension line of the one adjacent edge afterthe OPC and the extension line of the line segment, which is moved inparallel and excluded from the object of the OPC.

[0061] In the example of FIG. 7C, the adjacent edge 43 after the OPC isextended in its line segment direction as shown by the arrow line 63.The minute slanting line 39 connected to the other edge 34 is moved inparallel in accordance with the correction value of the edge 34, andconnected to the adjacent edge 44 after the OPC. The slanting line afterthe parallel movement 39 is extended in its line segment direction asshown by the arrow line 69. These two extension lines are connected atthe intersection point I. As a result, the pattern 60 after thecorrection, which does not include minute hollows and acute portions atall, is obtained by the very simple processing.

[0062] Also in the second embodiment, like the first embodiment, it isunnecessary to determine the correction value with individualsimulations for the minute portions. The correction pattern can beprepared by the simple processing in a short time by use of the resultsobtained by the ordinary OPC processing. Furthermore, acute shapes andminute unevenness, which are problems in checking the mask, are neverleft.

[0063] Similarly to the first embodiment, the processing illustrated inFIGS. 5C to 5D, in FIGS. 6A and 6B and FIG. 7C may be combined with theOPC processing, or alternatively performed separately from the OPCprocessing.

[0064] Third Embodiment

[0065]FIGS. 8A to 8E illustrate another correction method of a designpattern including a minute slanting step difference. In the secondembodiment, when the design pattern includes the slanting stepdifference, the mask pattern was generated by the simple method whileutilizing the slanting lines in the design data.

[0066] In the third embodiment, a pattern correction method for the casewhere slanting lines has almost no important significance on design datain an actual pattern transferred onto a wafer is provided.

[0067] As shown in FIG. 8B, the minute slanting lines 37, 38 and 39,which are excluded from the objects of the OPC, are first transformed tothe pattern parallel with the rectangular coordinate axis. Thus, thepattern 45 composed of only the edges in the X and Y-directions isobtained as shown in FIG. 8C. The transform of the slanting lines to thepattern in the directions of the rectangular coordinate axes shown inFIGS. 8B and 8C may be executed as pre-processing prior to the OPCprocessing, or alternatively may be combined with the OPC processing.

[0068] Next, as shown in FIG. 8D, the ordinary OPC processing is excutedfor the pattern 45 which does not include a slanting step difference. Asa result, the mask pattern 49 which does not include minute unevennessand acute portions is obtained.

[0069] For the sake of comparison with the above, the pattern of FIG. 8Eis obtained in the case where the pre-processing is not executed for thepattern 30 of FIG. 8A and only the conventional OPC processing isexecuted. When the conventional OPC processing alone is executed,undesirable acute projections and hollows occur, as shown in a circle C,and they decrease precision of a mask drawing, and they cause asuspected failure in checking the mask, thus causing erroneous check.

[0070] While, the method shown in FIGS. 8A to 8D can generate a maskpattern suitable for a mask drawing and a check, with simple processinglike the first and second embodiments. Furthermore, since the slantinglines are transformed to the line segments along the rectangularcoordinate axis in the third embodiment, an amount of data processingafter the transform is decreased, and a correction time is shortened.

[0071] Fourth Embodiment

[0072]FIGS. 9A to 9C illustrate a pattern correction method according toa fourth embodiment of the present invention.

[0073] In the fourth embodiment, the pattern correction method in thecase where violation against rules is detected in rule check after thepattern correction is shown. Usually, the OPC processing is executed foreach pattern, and after one pattern is corrected, it is checked whetheror not the corrected pattern meets a predetermined design rule. Evenwhen the pattern correction itself is proper, the corrected pattern issometimes against the design rule because of the positional relationbetween the corrected pattern and peripheral patterns, and the like.

[0074] For example, the case where the peripheral pattern 72 exists nearthe pattern 70 including a minute step difference on design data, asshown in FIG. 9A, is considered. It is assumed that the correctionprocessing is executed for the aimed pattern 70 by use of the methodillustrated in FIGS. 5A to 5D of the second embodiment, and the pattern75 illustrated in FIG. 9B is obtained. In this case, the shape of themask pattern 75 is a good pattern shape, which does not cause erroneousdetection and takes an optical proximity effect into consideration.

[0075] Herein, rule check is executed for the corrected pattern 75, andit is verified whether the corrected pattern accords to the mask designrule. In the example of FIG. 9B, since the peripheral pattern 72 islocated in the vicinity of the pattern 75, the patterns 72 and 75 areclose to each other. When exposing is performed practically, the twopatterns are likely to be short-circuited by coupling.

[0076] The positional relation between the two patterns 72 and 75 isconsidered in view of the shortest distance between the peripheralpattern 72 and the corrected pattern 75. Alternatively, the positionalrelation between them may be decided depending on whether or not the twopatterns 72 and 75 are located within a range of a predetermineddistance. For example, if the gap d3 is smaller than a predeterminedthreshold value in the mask design rule, the gap d3 being formed betweenthe apex V1 in the corrected pattern 75, which is closest to theperipheral pattern 72, and the apex V2 in the peripheral pattern 72, thecorrected pattern 75 is detected as the one which violates the designrule.

[0077] Accordingly, when the violation of the design rule is detected,correction processing is executed for the aimed pattern 70 by analternative method as shown in FIG. 9C, and the aimed pattern 70 istransformed to a shape meeting the design rule. Specifically, the designpattern 70 is corrected by use of another alternative method, forexample, the method of the second embodiment shown in FIGS. 5A to 5D, instead of the pattern correction executed in FIG. 9B. By use of themethod shown in FIGS. 7A to 7C specifically, by use of the method toconnect the pattern at the intersection point I of the extension line 73a of the adjacent edge 73 after the OPC on one side of the slanting stepdifference and the extension line 79 after the parallel movementextending from the other adjacent edge, the corrected pattern 80 inaccordance with the design rule is generated.

[0078] In the example shown in FIGS. 9A to 9C, the optical proximityeffect correction is executed for the pattern 70 including the slantingstep difference. When the design pattern is composed of only rectangularpattern, the method illustrated in FIG. 3 or FIG. 4 of the firstembodiment may be adopted as an alternative corrective method after therule check.

[0079]FIG. 10 illustrates a flowchart of the pattern correctionprocessing of the fourth embodiment, which includes the foregoing rulecheck. First, in step S801, design data for use in a mask of an objectlayer for correction is inputted. Semiconductor devices and liquidcrystal panels have a multilayered structure in which transistors andwiring layers are formed over many layers, and the mask pattern is alsodesigned and prepared for the respective layers. The optical proximityeffect correction for the design data is executed for each layer.

[0080] Next, as shown in step S803, an edge which meets predeterminedconditions and is intended to be an object of the OPC processing iscorrected. This correction is an ordinary OPC processing.

[0081] Subsequently, in step S805, a correction (transformation) isexecuted for a minute edge and a minute slanting step difference, whichdo not meet the predetermined conditions. For example, since the edge isshorter than predetermined length, it is excluded from the object of theOPC processing. The edge is referred to as a minute edge in FIG. 10.Such the minute edge is transformed by use of a first method selectedfrom any one of the methods shown in the first and second embodiments.

[0082] To be concrete, as the first method, used are any one of themethods including (1) the one shown in FIGS. 3A to 3C, in which theminute edge is made to be coincident with one adjacent edge; (2) the oneshown in FIGS. 4A to 4C, in which the minute edge is virtually split atthe midpoint thereof and made to be respectively coincident with each ofadjacent edges; (3) the one shown in FIGS. 5A to 5D, in which the minuteslanting step difference is moved in parallel as it is, and connected tothe extension lines of the adjacent edges; and (4) the one shown inFIGS. 7A and 7C, in which the slanting edge connected to one adjacentedge is moved in parallel, and the other adjacent edge is extended to beconnected thereto at the intersection point.

[0083] Next, in step S807, it is decided for each minute edge whetherthe pattern after the correction (transformation) meets the mask designrule or not. If the pattern after the correction meets the mask designrule, that is “YES” in step S807, the procedure advances to step S815.It is verified whether there are minute edges that have not undergonethe rule check yet. If there is a minute edge that has not undergone therule check, the procedure returns to step S807, the rule check isexecuted for the next minute edge.

[0084] In step S807, if the pattern after the correction does not meetthe design rule, that is “NO” in step S807, the procedure advances tostep S809, and another method is selected from the methods shown inFIGS. 3A to 3C, FIGS. 4A to 4C, FIGS. 5A to 5D, and FIGS. 7A to 7C, andthe correction (transformation) is tried for the aimed minute edge. Amethod used herein is called a second method.

[0085] After a correction by use of the second method, the rule check isagain executed in step S811. If the pattern after the correction by useof the second method comes to meet the rule check, that is “YES” in stepS811, the procedure advances to step S815. If there is a minute edgewhich has not undergone yet, the processing from step S807 onward arerepeatedly executed.

[0086] If the pattern after the correction does not meet the design rulein spite of the execution of the correction by use of the second method,that is “NO” in S811, the procedure advances to step S813, and stillanother method is selected from the foregoing methods. Then thecorrection (transformation) is tried. The method used herein is called athird method.

[0087] After the correction (transformation) by the third method, it isdecided in step S815 whether or not the rule check has been finished forall minute edges, and steps S807 to S815 are repeatedly executed untilprocessing is finished for all minute edges.

[0088] In this method, without determining the correction valueindividually by simulation, it is possible to correct all minute edgesincluded in the pattern so that the pattern is made to meet the maskdesign rule. Furthermore, since any of the methods shown in the firstand second embodiments is used, undesirable minute unevenness and acutepattern never occur by the correction.

[0089] Although not illustrated, before the step S803 as required, thepre-processing shown in the third embodiment may be executed for someaimed pattern. That is, a processing may be executed for transforming aminute slanting step difference, which has no significance as a patternshape on a wafer, to a pattern parallel with a rectangular coordinateaxis. By inserting or incorporating this pre-processing, the processingafter that becomes simpler.

[0090]FIGS. 11A to 11C illustrate the variation of the patterncorrection method after the rule check. In the method shown in FIGS. 9Ato 9C and FIG. 10, the violation of the design rule is avoided by use ofthe alternative method while paying attention to the shape of the designpattern.

[0091] In the method illustrated in FIGS. 11A to 11C, when the violationof the design rule is detected, an area violating the design rule is cutaway. This method is effective in the case where a step difference and aminute slanting line, which exist on design data, has no almostsignificance when they are transferred on a wafer.

[0092] As shown in FIGS. 11A and 11B, when the aimed pattern 70 iscorrected by the method of the second embodiment shown in FIGS. 5A to5D, it is assumed that the violation against the mask design rule isdetected at the distance d3 between the pattern 80 which is a correctedpattern and the peripheral pattern 72 located near the pattern 80.

[0093] In FIG. 11C, the whole of the projection area D close to theperipheral pattern 72 is cut away by the line segment 77 in theX-direction and the line segment 78 in the Y-direction. The cut-awayline segments 77 and 78 are respectively connected to the adjacent edges73, 74 after the OPC processing, thus constituting the pattern 81 afterthe correction, which meets the design rule. The pattern 81 after thecorrection is corrected to a shape suitable for the mask drawing and thecheck without significant effect on the transferred shape on the wafer.

[0094]FIG. 12 is a processing flowchart of the pattern correction methodillustrated in FIGS. 11A to 11C.

[0095] First, in step S901, the mask design data for the correctionobject layer is inputted. In step S903, as to an aimed pattern, an edgemeeting the predetermined conditions and being targeted for the OPCprocessing is corrected. This correction is an ordinary OPC processing.

[0096] Next, in step S905, the correction (transformation) is executedfor a minute edge and a minute slanting step difference which isexcluded from an object of the OPC because of the reason why they areshorter than a predetermined length and of other reasons.

[0097] Next, in step S907, for each minute edge, it is decided whetheror not the pattern after the correction (transformation) meets the maskdesign rule. If the pattern meets the design rule, that is “YES” in stepS907, the procedure advances to step S911, it is verified whether aminute edge that has not undergone the rule check yet exists or not.When there is the minute edge that has not undergone the rule check yet,the procedure returns to step S907, and the rule check is executed for anext minute edge.

[0098] In step S907, if the pattern after the correction(transformation) does not meet the design rule, that is “NO” in S907,the procedure advances to step S909, and an area corresponding to theviolation of the rule is cut away.

[0099] Finally, in step S911, it is verified whether the rule check hasbeen executed for all minute edges, and if there is a minute edge thathas not undergone the rule check yet, the processing from step S907onward is repeated.

[0100] The cut-away correction for the rule violation spot shown in FIG.11C may be executed in stead of step S813 in the alternative methodshown in FIGS. 9C and 10. Alternatively, the cut-away correction may beinserted in the step after the step S813. Thus, areas violating thedesign rule can be surely excluded from the mask pattern.

[0101] Fifth Embodiment

[0102]FIGS. 13A to 13G and FIGS. 14A to 14G illustrate a patterncorrection method according to a fifth embodiment of the presentinvention.

[0103] In the fifth embodiment, provided is a method for erasing minutepattern not affecting a transferred image onto a wafer by biasprocessing and simple logic operation processing when a design patternafter OPC processing includes them.

[0104] As described above, a pattern after the OPC processing oftenincludes minute unevenness. The unevenness adversely affects a maskdrawing and a check in spite of the fact that it hardly has anyinfluence on a transferred image onto a wafer. Therefore, the minuteunevenness should be erased and flattened.

[0105] However, the conventional correction method creates new acutenotches and acute projections in the course of erasing the minuteunevenness. Accordingly, in the fifth embodiment, a mask pattern iscorrected to a shape suitable for a mask drawing and a check with asmall processing amount without leaving these acute portions.Particularly, in FIGS. 13A to 13G, a method for effectively erasing theacute notches created during a repairing stage after the OPC isillustrated. In FIGS. 14A to 14G, a method for eliminating the acuteprojections is illustrated.

[0106] First, as shown in FIG. 13A, the pattern 85 is obtained by anordinary OPC processing. Herein, it is detected whether or not thepattern 85 after the OPC processing includes minute unevenness. In thisdetection, determination is made, for example, depending on whether ornot an aimed pattern includes unevenness which does not meet conditionspredetermined in accordance with a line width and a line length thereofand the like. Herein, minute hollows and minute projections of 0.1 μm orless shall be a minute pattern.

[0107] In the case of FIG. 13A, the pattern 85 after the OPC processingincludes the minute unevenness 86 and 87. Accordingly, a slightly thickbias and a slightly thin bias respectively shown in FIGS. 13B and 13Care continuously applied to the pattern 85 (slightly thick/slightly thinbias), and the minute hollow 86 is erased. To be concrete, the pattern85 is made to be thicker by 0.05 μm in FIG. 13B, and the thickenedpattern 88 is made to be thinner by 0.05 μm in FIG. 13C.

[0108] The pattern 89 in which the minute hollow 86 is erased isobtained by the slightly thick/slightly thin bias processing. However,as a result of the bias processing, the acute notch E newly occurs. Sucha notch like the notch E causes an erroneous detection in the maskdrawing and the check and is undesirable.

[0109] Accordingly, as shown in FIGS. 13D and 13E, the notch E isburied, and the pattern 91 in which the notch is erased is obtained. Theerasure of the notch is realized in such a manner that a “FIG. 13A NOTFIG. 13C” operation is executed to get the state of FIG. 13D, and a“FIG. 13C OR FIG. 13D” operation is executed. The shape in FIG. 13E isobtained by the operations.

[0110] The minute hollows 86 can be erased by the processing until FIG.13E without creating unnecessary acute portions in the pattern 85 afterthe OPC processing.

[0111] Next, as shown in FIGS. 13F and 13G, the remaining minuteprojection 87 is erased by applying a slightly thick/slightly thin biasto the pattern. Specifically, the pattern 91 obtained in FIG. 13E ismade to be thinner by 0.05 μm, and the state of the pattern 93 in FIG.13F is obtained. The pattern 93 is further made to be thicker by 0.05μm, whereby the final pattern 94 illustrated in FIG. 13G is obtained.

[0112] As described above, by applying the proper repair to the patternafter the OPC processing, the minute unevenness can be effectivelyerased.

[0113] An example in which an acute projection is erased is shown inFIGS. 14A to 14G. In this example, the pattern 100 after the OPCprocessing, which has the minute hollow 101 and the minute projection102 to be subjected to repair.

[0114] First, the slightly thick/slightly thin bias processing in whichthe pattern 100 is sequentially made to be thicker and thinner by 0.05μm is executed for the pattern 100 from FIGS. 14A to 14C like FIGS. 13Ato 13C. The pattern 103 in which the minute hollow 101 is erased isobtained by these processing.

[0115] Next, as shown in FIGS. 14D and 14E, the slightly thick/slightlythin bias processing of 0.05 μm is executed for the pattern 103.

[0116] The pattern 107 of FIG. 14D, in which the minute projection 102is erased, is obtained by the slightly thick/slightly thin biasprocessing. However, the acute projection F is newly created. The acuteprojection F created during the repairing step can not be erased by theconventional method, and may cause a suspected failure in the maskdrawing and the check

[0117] Accordingly, as shown in FIGS. 14F and 14G, a “FIG. 14E NOT FIG.14C” operation is executed, thus getting the state of FIG. 14F, and thena “FIG. 14E NOT FIG. 14F” operation is further executed.

[0118] Thus, the good pattern shape 109 in which the minute hollow 101and the minute projection 102 are erased from the pattern 100 after theOPC processing is obtained without creating undesirable acuteprojections.

[0119] The acute notches and hollows, which are created during therepairing step after the OPC processing, can be simply erased with asmall operation amount by properly using the foregoing bias repair andlogic operations. Thus, the pattern correction suitable for the maskdrawing and the check can be executed.

[0120] In the descriptions for the fifth embodiment, the case where thepattern repair is executed after the OPC processing was made. However,the pattern repair can be incorporated in the OPC processing.

[0121] Any of the methods shown in the first to fifth embodiments can bedirectly installed as a pattern correction program in a patterngeneration/correction apparatus such as a CAD, either by beingincorporated in an ordinary OPC or independently from the ordinary OPC.This program may be once stored in a magnetic disc, an optical disc, amagneto-optical disc (MO disc), a magnetic tape, floppy disc, CD-ROM,cassette tape and the like.

[0122] The present invention was hitherto described based on theembodiments, and the present invention is not limited to the foregoingembodiments. Combinations of the embodiments are possible according todemand. For example, a program can be made so that the preprocessingshown in the third embodiment is followed by the ordinary OPC, and thepattern correction meeting the design rule of the fourth embodiment isexecuted. In addition to this, a program may be made so that the biasprocessing of the fifth embodiment is executed after the ordinary OPCprocessing.

[0123] When a semiconductor device is manufactured by use of suchpattern correction method, first a pattern to be formed on asemiconductor wafer is designed for each layer. The optical proximityeffect correction shown in the first to fifth embodiments is executedfor the designed pattern, thus preparing mask data. A mask for eachlayer is manufactured based on the mask data. The pattern is transferredonto the semiconductor wafer by use of the manufactured mask.

[0124] Harmful results such as pattern-shrink caused by exposing can beprevented by use of such manufacturing method of the semiconductordevice.

[0125] As described above, according to the correction method of thepresent invention, without executing simulations individually, thepattern correction can be executed with simple processing in a shorttime for minute edges and minute unevenness that are excluded fromobjects of the OPC.

[0126] Furthermore, since new unevenness and acute portions are notcreated during the pattern correction steps, the erroneous detection inthe mask drawing and the check can be prevented.

[0127] Still furthermore, since the pattern is corrected so as to meetthe mask design rule, the final mask pattern suitable for the maskmanufacture can be obtained.

What is claimed is:
 1. A pattern correction method executed by acomputer the method comprising: executing a first correction for one ora plurality of first edges meeting a condition among the edgesconstituting a designed pattern, by calculating correction values inconsideration for an optical proximity and correcting the one or aplurality of first edges with the calculated correction values;executing a second correction for a second edge which does not meet thecondition, by correcting the second edge with the correction value ofany one of the first edges adjacent to the second edge among the firstedges for which the first correction is executed; and connecting thecorrected first edge and the corrected second edge by a line segment. 2.The pattern correction method according to claim 1, wherein the secondcorrection comprises: correcting the second edge by making it becoincident with the correction value of the first edge adjacent to oneside of the second edge; and connecting an end portion of the other sideof the corrected second edge and another corrected first edge adjacentto the other side of the corrected second edge, by a line segment. 3.The pattern correction method according to claim 1, wherein the secondcorrection comprises: obtaining a first line segment by making a half ofthe second edge which is one side relative to a midpoint thereof becoincident with the correction value of the first edge after the firstcorrection adjacent to the one side of the second edge; obtaining asecond line segment by making the remaining half of the second edgewhich is the other side relative to the midpoint thereof be coincidentwith the correction value of another first edge after the firstcorrection adjacent to the other side of the second edge; and connectingthe fist and second line segments with a line segment passing throughthe midpoint
 4. The pattern correction method according to claim 1,wherein the second correction comprises: moving the second edge inparallel so that the second edge is made to be coincident with thecorrection value of the first edge adjacent to one side of the secondedge; extending another first edge adjacent to the other side of thesecond edge, in a direction of a line segment of the another first edge;and connecting the second edge moved in parallel and the first edgeextended, to each other at a point of intersection of these first andsecond edges.
 5. The pattern correction method according to claim 1,wherein the second correction is executed by one method selected fromthe following methods: (1) a first method comprising: correcting thesecond edge by making it be coincident with the correction value of thefirst edge adjacent to one side of the second edge; and connecting anend portion of the other side of the corrected second edge and anothercorrected first edge adjacent to the other side of the corrected secondedge, by a line segment; (2) a second method comprising: obtaining afirst line segment by making a half of the second edge which is one siderelative to a midpoint thereof be coincident with the correction valueof the first edge after the first correction adjacent to the one side ofthe second edge; obtaining a second line segment by making the remaininghalf of the second edge which is the other side relative to the midpointthereof be coincident with the correction value of another first edgeafter the first correction adjacent to the other side of the secondedge; and connecting the fist and second line segments with a linesegment passing through the midpoint; (3) a third method, comprisingmoving the second edge in parallel so that the second edge is made to becoincident with the correction value of the first edge adjacent to oneside of the second edge; extending another first edge adjacent to theother side of the second edge, in a direction of a line segment of theanother first edge; and connecting the second edge moved in parallel andthe first edge extended, to each other at a point of intersection ofthese first and second edges; after the second correction, the patterncorrection method further comprising: deciding whether or not a patternafter the second correction meets a design rule; and executing a thirdcorrection for the second edge by use of another method among themethods (1) to (3) different from a method selected in the secondcorrection, when the pattern after the second correction does not meetthe design rule.
 6. The pattern correction method according to claim 1,after the second correction, the pattern correction method furthercomprising: deciding whether or not a pattern after the secondcorrection meets a design rule; and cutting away a spot violating thedesign rule when the pattern after the second correction does not meetthe design rule.
 7. The pattern correction method according to claim 6,wherein the cut away processing is executed in a manner that the spot iscut away at an extension line of the adjacent edge which has beenundergone the first correction, the extension line being adjacent to thespot which does not meet the design rule.
 8. The pattern correctionmethod according to claim 1, the method further comprising: transformingall of the first edges which do not meet the condition to edges mparallel with rectangular coordinates axis, before the first correction.9. The pattern correction method according to claim 1, wherein thecondition is that a length of an edge is equal to a certain value ormore.
 10. The pattern correction method according to claim 1, whereinthe correction value of the first correction is calculated by asimulation.
 11. A pattern correction method executed by a computer, themethod comprising: designing a pattern to be formed on a wafer;executing a correction for at least one of edges meeting the conditionamong the edges constituting the designed pattern in consideration foran optical proximity effect; deciding whether or not the correctedpattern includes minute pattern having no effect on a transferred imageonto the wafer; executing bias processing in combination of bias forthickening the whole of the pattern after the correction and bias forthinning bias it when the corrected pattern includes the minute pattern;and executing a logic operation after the bias processing, thus erasingan acute pattern caused by the bias processing.
 12. A manufacturingmethod of a semiconductor device comprising: preparing design data inwhich patterns to be formed on a semiconductor wafer are designed forrespective layers; inputting the design data for each layer, thuspreparing mask data for each pattern included in the design data, thepreparing the mask data including: (1) executing a first correction bycalculating correction values for at least one of first edges meeting acondition in consideration for an optical proximity effect; and (2)executing a second correction for a second edge which does not meet thecondition, by use of the correction value of the first edge adjacent tothe second edge, thus connecting the corrected first edge and thecorrected second edge; preparing a mask based on the mask data; andtransferring the pattern onto the semiconductor wafer by use of themask.
 13. A manufacturing method of a semiconductor device comprising:preparing design data in which patterns to be formed on a semiconductorwafer are designed for respective layers; inputting the design data foreach layer, thus preparing mask data for each pattern included in thedesign data, the preparing the mask data including the following (1) to(4): (1) executing a correction for edges meeting a condition inconsideration for an optical proximity effect; (2) deciding whether ornot the pattern after the correction includes minute pattern having noeffect on a transferred image onto the wafer; (3) executing biasprocessing in combination of bias for thickening the whole of thepattern after the correction and bias for thinning it when the correctedpattern includes the minute pattern and (4) executing a logic operationafter the bias processing, thus erasing an acute pattern caused by thebias processing; preparing a mask based on the mask data; andtransferring the pattern onto the semiconductor wafer by use of themask.
 14. A computer program product configured to be executed by acomputer, the program product comprising: executing a first correctionfor one or a plurality of first edges meeting a condition among theedges constituting a designed pattern, by calculating correction valuesin consideration for an optical proxmity and correcting the one or aplurality of first edges with the calculated correction values;executing a second correction for a second edge which does not meet thecondition, by correcting the second edge with the correction value ofany one of the first edges adjacent to the second edge among the firstedges for which the first correction is executed; and connecting thecorrected first edge and the corrected second edge by a line segment.15. A computer program product configured to be executed by a computer,the program product comprising: designing a pattern to be formed on awafer; executing a correction for at least one of edges meeting thecondition among the edges constituting the designed pattern inconsideration for an optical proximity effect; deciding whether or notthe corrected pattern includes minute pattern having no effect on atransferred image onto the wafer; executing bias processing incombination of bias for thickening the whole of the pattern after thecorrection and bias for thinning bias it when the corrected patternincludes the minute pattern; and executing a logic operation after thebias processing, thus erasing an acute pattern caused by the biasprocessing.